Development of Thermoelectric Materials Using Electron Localization Effects in Cluster Semiconductors

β-菱面体硼(β-Bobon)是纯硼的一种晶型，主要由B_(12)&gt；二十面体簇合物组成。为了寻找β-B中提高ZT的条件，用ZT=σS^2T/κ表示，我们研究了不同金属原子(V、Co、Ni、Cu、Fe、SR、Zr或W)掺杂后，热电参数σ、S和κ从20K到1073K的变化。利用电弧炉熔炼和热压样品的数据分析了显微组织对组织的影响。成功地掺杂了V、Co、Ni、Cu、Fe和Zr，并且第二相的数量很少。热压样品的σ和S与电弧炉熔炼的样品相差不大，但由于其多孔结构或细小的晶粒尺寸，热压样品的κ小于电弧炉熔炼样品。尤其是V原子主要占据β-B的A_1位的V掺杂热压样品，σ大大增加，S甚至减小到负值，κ减小。本研究中的最大n型ZT值为o…对于V掺杂的热压样品，更接近于被认为是富硼二十面体团簇固体中最大的p型ZT值的B_4C。我们研究了AlPdRe二十面体合金的Seebeck系数和电导率与成分的关系。随着过渡金属(Pd或Re)浓度的增加，Seebeck系数迅速增大。这种强烈的成分依赖性与费米能级电子态密度中的赝隙结构有关，也与Al与过渡金属成键性质的变化有关。还观察到了导热过程中的玻璃态输运行为。在600-700K温度范围内，无因次热电优值的最大值约为0.1，表现出强烈的成分依赖性。研究了在AlPdRe二十面体准晶中用Ru取代Re的四元AlPdReRu准晶的热电性质。在Ru替代Re的过程中，电导率随温度的升高而增大，Seebeck系数的峰值向高温侧移动。在AlPdRe准晶中加入Ru后，无因次优值ZT提高了1.5倍。较少

β-Rhombohedral boron(β-boron) is one of polymorphs of pure boron which consists mainly of B_<12> icosahedral clusters. To search the condition in β-boron to enhance ZT, which is represented by ZT=σS^2T/κ, we investigated the change of the thermoelectric parameters, σ, S and κ, from 20K to 1073K when various metal atom(V, Co, Ni, Cu, Fe, Sr, Zr or W) was doped. The data for arc-melted and hot-pressed samples were used to see the effect of micro-structure. V, Co, Ni, Cu, Fe and Zr are successfully doped and the amount of second phases are very small. While there is only little difference on σ and S between hot-pressed and arc-melted samples, κ for hot-pressed sample is smaller than that for arc-melted one because of its porous structure or small grain size. Especially, for the V doped hot-pressed sample, in which V atoms mainly occupy A_1 site of β-boron, σ is increased very much, S is decreased even to negative value and κ is decreased. The maximum and n-type ZT value in this study is o … More btained for the V doped hot-pressed sample and is approaching to that of B_4C which is considered to have the largest and p-type ZT value in boron-rich icosahedral cluster solids.We investigated the composition dependence of the Seebeck coefficient and the electrical conductivity of AlPdRe icosahedral alloys. As the concentration of transition metal (either Pd or Re) increases, the Seebeck coefficient rapidly increases. The strong composition dependence is related to the pseudogap structure in the electron density of states at the Fermi energy, and to the variation in bonding nature between Al and transition metal. Glass-like transport behavior in thermal conduction is also observed. The dimensionless thermoelectric figure of merit has a maximum value of approximately 0.1 in the temperature range from 600 to 700 K and reveals strong composition dependence. Thermoelectric properties of the quaternary AlPdReRu quasicrystal that replaced Re by Ru in AlPdRe icosahedral quasicrystals have been studied. In the middle of substitution Ru for Re, the electrical conductivity increases with increasing temperature and the peak of Seebeck coefficient shifts to a higher temperature side. By Ru addition to the AlPdRe quasicrystal, value of dimensionless figure of merit, ZT, goes up 1.5 times. Less